Energy storage systems, such as, lithium-ion batteries, are widely used as portable power sources for consumer electronic devices because of their high energy density and flexible design. While graphite is widely used commercially as an anode, i.e., negative electrode, materials in lithium-ion batteries, there is an interest in the art to identify intermetallic materials as potential alternative anode materials with higher capacity, cycle life, and lower irreversibility. Binary and multi-component lithium alloy systems have been considered, which can include tin, silicon, aluminum, antimony (i.e., Sn, Si, Al and Sb, respectively) and mixtures thereof. However, there are concerns associated with these zintl phase systems. In general, with the use of tin, silicon, aluminum, antimony and mixtures thereof, a large volume change can occur during charge/discharge which may result in cracking and crumbling of the anode. This can lead to loss of electrical contact between the active element particles which may cause mechanical failure of the electrode. As a result, the cyclability of the electrode can be severely limited.
For example, silicon may be considered a potential lithium-ion battery anode material to replace the current graphite anode due to its high capacity and abundance in resource. However, application of a silicon anode may be hindered by the rapid capacity decay with cycling. There can be large volume changes associated with various phase transitions occurring during the lithium alloying and de-alloying processes. Thus, there is a resulting potential for decrepitation and breakdown of an electronic contact network in the electrode.
Various techniques have been identified for preparing suitable one-dimensional (1D) nano-structure anode materials, including decomposition of organic precursors, high energy mechanical milling (HEMM), chemical vapor deposition, sputtering, physical mixing, and carbon coating on silicon particles.
The methods used to produce silicon thin film anode materials having good cycling performance include vapor phase deposition methods such as pulsed laser deposition (PLD), sputtering, and molecular beam epitaxy which may not be commercially feasible due to the high cost and low yield of these processes.
The process of slurry mixing and casting of 1D nano-structure anode materials to fabricate electrode films can diminish the advantages provided by the 1D nano-structure anode materials. For example, the addition of polymer binder and carbon black may reduce the diffusion distances, and may also create unwanted additional interfaces thereby increasing the ionic impedance and electronic resistance. The slow kinetics within the polymer binder interface between the active materials and substrate may be an obstacle to attaining the intrinsic characteristics of the anode material while limiting the rate capability of the battery.
There is a need to develop rechargeable lithium-ion batteries with higher energy density and longer service life to power for use in diverse applications including electronic devices, electric vehicles, intermittent power source storage, and implantable energy systems and the like. Further, there is a need to develop an anode material including a nano-scale composition for use in energy storage applications. Furthermore, there is a need to employ 1D nano-structures in the preparation process of electrodes to preserve the configuration and morphology, and therefore the benefits, of the nano-scale anode material. Moreover, there is a need to generate an anode exhibiting a stable reversible capacity, e.g., of above 1000 mAh/g, with a silicon and carbon composite material.